An agricultural harvester, such as a combine or windrower, is a large machine used to harvest a variety of crops from a field. In the case of a combine, during a harvesting operation, a header at the front of the combine cuts ripened crop from the field. A feeder housing supporting the header transfers the crop material into the combine. Threshing and separating assemblies within the combine remove grain from the crop material and transfer the clean grain to a grain tank for temporary holding. Crop material other than grain exits from the rear of the combine. An unloading auger transfers the clean grain from the grain tank to a truck or grain cart for transport, or to another receiving bin for holding.
In the case of a windrower, during a harvesting operation, a header at the front of the windrower cuts ripened crop from the field. The crop is transported to the rear of the header and forming shields form a windrow of the crop between the tires of the vehicle for natural dry down of the crop. A subsequent field operation picks up the windrows for further processing, such as separating and cleaning in the case of grain crops, or baling or chopping in the case of hay.
Platform headers and draper headers are header types commonly used when harvesting crops such as small grains, peas, lentils, and rice. During a harvesting operation with these header types, it is desirable to maintain a predetermined cutting height. To accomplish this, it is known to use a header float system or a terrain following system to enable the header to follow the ground over changing terrain without gouging or digging into the soil.
Manufacturers have developed a number of header float systems for use on harvesters such as combines, windrowers, etc. over the years. U.S. Pat. Nos. 3,717,995, 3,623,304, and 4,724,661 disclose examples of header float systems using a resilient suspension to suspend the header, thereby reducing the apparent weight of the header, allowing it to lightly skid across the ground over changing terrain. U.S. Pat. Nos. 3,597,907, 4,622,803 and 5,471,823 disclose examples of similar float systems, but using a dynamic suspension to suspend the header. U.S. Pat. Nos. 5,577,373, 6,041,583 and 6,758,029 B2 disclose examples of terrain following systems which dynamically position the header, thereby sensing and changing the vertical position of the header to follow changing terrain.
What is needed in the art is a float system for a header which accommodates both cutting height and tilt on the header, and load distribution between the header and traction unit.